Radiant tubular heat exchanger



Sept. 1, 1959 G. STEINERT 2,902,010

RADIANT TUBULAR HEAT EXCHANGER Filed Aug. 19, 1957 FIG. I FIG. 2 v

' INVENTOR.

GERHARD STEINERT ATTORNEY United States Patent TUBULAR HEAT EXCHANGERGerhard Steinert, Stuttgart, Germany, assignor toKohlenscheidungs-Gesellschaft, m.b.H., a corporation of GermanyApplication August 19, 1957, Serial No. 679,048

Claims. (Cl. 122-23i5) The invention relates to a tubular heat exchangerof, the cyclonic type and is particularly concerned with a steamgenerator having one or several combustion or slagging chambers and aradiant heat absorbing chamber arranged immediately thereabove andhaving a gas outlet duct leading from the combustion chamber 'into theradiation chamber said duct extending downwardly into the combustionchamber in the form of a sleeve; and wherein the combustion chamber,radiation chamher and gas outlet duct are lined with steam generatingtubes.

In conventional designs of cyclonic steam generators of this typeconsiderable difficulties have been experi- "enced in accommodating thetubes lining the combustion chamber and tubes of which the gas outletduct is formed, within the available wall space of the radiationchamber. These diificulties have made it necessary in 'the past toemploy tube designs of great complexity and of high manufacturing andinstallation costs.

The present invention provides a simple water wall constructionaifording important advantages in the design of the tubular wall liningsfor cyclonic radiant steam generators. Such improvements include theprovision of an intermediate horizontal header located at an elevationintermediate the combustion chamber and the radiation chamber forreceiving the wall tubes of the combustion chamber and from which headerany desired number of tubes can originate to supplement the tubularlining of the walls of the radiation chamber, a

'gas outlet duct leading from the combustion chamber to the radiationchamber.

The inventive design provides for greater flexibility and independencein the number of tubes employed for each furnace component, therebyavoiding the possible forming of bottle necks in the circulation systemand preventing the creation of hot spots and the resulting failure oftubes due to inadequate circulation of water.

In addition the present invention makes it possible to considerablysimplify the construction of the furnace. 'It permits prefabricati'on ofportions of the furnace in the shops and thus facilitates speed oferection of the steam generator in the field.

A further advantage of this design resides in the use of the above namedintermediate header for supplying platen type heating surfaces suspendedwithin the radiation chamber with the working fluid such as steam orwater. In this manner it is possible to enlarge to a considerable extentthe eflective heating surface in the radiation chamber without the useof additional special headers and supply tubes. A substantial reductionin overall size of the heat exchanger can thereby be achieved.

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Additional objects and advantages of the invention will become apparentfrom the following description of an illustrative embodiment thereofwhen taken in conjunction with the accompanying drawing showing in Fig.-1 anel'eavtionalsection through a steam generator'equipped with myinventive improvement and in Fig. 2 a plan cross section taken on line2-2 of Fig. 1.

The steam generator illustrated is provided "with a cyclonic combustionchamber or slagging chamber 1 having a coaxially arranged gas outlet 2leading into an adjacent radiation chamber 3 disposed above said gasbutlet. Both the slagging chamber 1 as well as the gas outlet 2 are ofcircular cross section. The radiation chamher '3, however, "has arectangular cross section, as shown in Fig. 2, to accommodate the widthof the gas passages which follow-the radiation chamber 3 with respect togas flow. The wall of'slagging chamber 1 is lined on the inside withsteam generating tubes 4. These tubes originate in water headers 5 andterminate in an intermediate header '6 located at an elevation directlyabove the combustion chamber 1.

The gas outlet duct 2 is formed of steam generating tubes 7 whichoriginate in a lower water wall header 8 and which are extended upwardlyto serve as a partial lining for the radiation chamber 3. Because of therectangular cross sectional configuration of radiation chamber 3 incontrast to the circular cross section of duct 2, more tubes are neededto cover the walls of chamber 3 than can be supplied by the extensionsof tubes 7 from duct 2. Tubes 7 therefore in serving as'a .partiallining for chamber 3 must be widely spaced. The spaces between the tubesare filled by tubes 9 originating in the intermediate header 6. Thustubes 9 receiving the working fluid from tubes 4 of the combustionchamber 1 provide an additional lining for the walls of the radiationchamber 3. 7

There are also tubes 10 leading from intermediate header 6 to a verticalheader 11. This header 11 serves as an inlet header for'tube panels orpartition Walls 12 which are disposed within and extend transverselyacross the width of "radiation chamber 3, as shown in Fig. 2,

and upwardly to the roof thereof. In the upper portion of radiationchamber 3 there are disposed in between panels 12 additional tubularwalls 13 which serve as the :lower end of gas passage 15 to conduct thecombustion gases to additional heating surfaces such as an air heater(not shown) and/or to a stack (not shown).

Feed water enters the steam generator by way of valves 19 andflows'through feed tubes 20 into economizer inlet header 21 and thencethrough economizer 17. Tubes 20 also function as hanger supportsfor'economizer 17. The upper ends of the economizer tubes are extended'to form wall tubes 22 lining the rear wall of gas passage 15. Thesetubes continue to line and support the 'roof 23 of the steam generatorand terminate in steam and water drum 24. The preheated water thusentering drum 24 passes downwardly through downtake tubes 25 intodistributing headers 5 and '8. The water rises from these headers andunder constant evaporation passes through tubes 4, 7, 9, 10 and 12, tobe discharged from these tubes into drum 24 as a mixture of Water andsteam. The steam thereupon is separated from the water within the drum24 by means well known in the art and passes through connecting tubes 27into convection superheater 16, the tubes of which terminate in outletheader 28. From this header the partially heated steam passes intoradiant superheater 13 which is provided with an outlet valve 29 throughwhich the steam is conducted by way of steam pipe 3% to a point of usesuch as a turbine (not shown). Downtake tubes 26 are provided betweenheaders 6 and to drain off water separated from the steam in header 6.

The furnace and gas passages of the steam generator are surrounded by arefractory wall 31 and a layer of insulation 32 which in turn is linedwith a metallic cas- The fuel and combustion air is introduced intocombustion chamber 1 by Way of burner nozzles 33 and 34 respectivelywhich are directed tangentially towards an imaginary firing circlelocated coaxially within slagging chamber 1. The fuel is consumed whilefollowing a spiral path downwardly and then upwardly into the mouth ofthe sleeve-like gas duct 2 as indicated by the arrows. The temperaturesattained by combustion of the fuel are maintained above the ash fusionpoint, thereby permitting the ash to be discharged in a fluid conditionthrough a centrally located slag outlet 35. Due to centrifugal forcecreated by the whirling of the gases most of the liquid ash is depositedon the walls of slagging chamber 1, flows down these walls due togravity and out through slag outlet 35 to drop into a water filled ashpit (not shown). Suitable ash conveying apparatus (not shown) serve toremove the chilled slag from the ash pit. In order to increase the heatretaining capacity of the tubes 4 lining the slagging chamber 1, thesetubes are provided with studs for the purpose of supporting a refractoryfiller lining. A similar lining is provided for the outside surface ofthe gas outlet duct 2.

The combustion gases after having been separated from the liquid ashpass through gas outlet duct 2 into radiation chamber 3 and after havinggiven off most of their heat to the heating surfaces over which theyflow, are withdrawn from the steam generator by way of duct 18 and bymeans of an induced draft fan (not shown) and are discharged into theatmosphere.

Although the herein disclosed invention has been described in connectionwith a natural circulation steam generator of the radiant type, beingfired preferably with pulverized coal, this invention can with equallybeneficial results be used in connection with a controlled ciri 1culation unit or with a once-through type steam generator. Furthermore,the invention could also be applied to a heat exchanger in which otherfluids besides water and steam are heated, such as air or gases. Also,the

invention could be employed in connection with furnaces burning suchfuels as black liquor or other comminuted fuels. Furthermore theinvention can also be practiced with equally beneficial results in aheat exchanger apparatus operating under pressurized firing.

Although the invention as herein above described is used in connectionwith a steam generator having but one combustion chamber dischargingcombustion gases into a radiation chamber, several of such combustionchambers can be employed, discharging their gases into one or moreradiation chambers.

While I have illustrated and described a preferred embodiment of myinvention, it is to be understood that such is merely illustrative andnot restrictive and that variations and modifications may be madetherein without departing from the spirit and scope of the invention. Itherefore do not wish to be limited to the precise details set forth butdesire to avail myself of such changes as fall within the purview of myinvention.

I claim:

1. In a steam generator arranged for cyclonic burning of a comminuatedfuel, having a combustion chamber and a radiation chamber disposedimmediately thereabove, a gas outlet leading from said combustionchamber into said radiation chamber and including a sleevelike gas ductextending downwardly into said combustion chamber, the combination of afirst set of vertical water wall tubes comprising the walls of said gasduct, said first tubes extending upwardly to form the inner lining for aportion of the wall of said radiation chamber; a second set of waterwall tubes extending upwardly said second tubes comprising the wall ofsaid combustion chamber, a header for receiving and communicating withthe upper ends of said second tubes; and a third set of water wall tubesextending from said header and communicating therewith, said third tubesforming an inner lining for a remaining portion of the wall of saidradiation chamber; additional heating surface being provided in saidradiation chamber, said heating surface taking the form of a verticaltubular partition wall extending transversely across said radiationchamber and subdividing said radiation chamber into a plurality of gasflow channels; and a fourth set of tubes connecting the lower end ofsaid tubular partition wall with said header for fluid flowtherethrough; means for circulating water through said first, second,third and fourth set of tubes and said header; and means for dischargingstreams of fuel and air into said combustion chamber for burningtherein.

2. An apparatus as defined in claim 1 wherein a first distributingheader is provided to which the lower ends of said first water walltubes are connected, a second distributing header to which said secondwater wall tubes are connected and means for feeding water to each ofsaid first and second distributing headers.

3. An apparatus according to claim 2 wherein a plurality of downtaketubes are provided connecting said intermediate header with said firstheader.

4. In a steam generator arranged for cyclonic burning of a comminutedfuel, having a combustion chamber and a radiation chamber arranged forserial gas flow in the order named; a gas outlet leading from saidcombustion chamber into said radiation chamber, said gas outletincluding a sleeve-like gas duct extending downwardly into saidcombustion chamber, the combination of a plurality of first verticalwater wall tubes comprising the walls of said gas duct, said first tubesextending upwardly to form the inner lining for a portion of the wall ofsaid radiation chamber; a second plurality of vertical water wall tubescomprising the wall of said combustion chamber, an intermediate headerfor operatively communicating with the upper ends of said second tubes;and a third plurality of water wall tubes extending from said header foroperative communication therewith, said third tubes forming an innerlining for a remaining portion of the wall of said radiation chamber; avertical tubular panel disposed within said combustion chamber forabsorption of heat, said tube panel taking the form of a partition wallextending transversely across said radiant chamber and subdividing saidradiant chamber into a plurality of gas flow channels; a fourth set oftubes establishing communication with the lower end of said tubularpanel and with said intermediate header for fluid flow therethrough; afirst distributing header operatively connected for fluid flow to thelower end of said first tubes; a second distributing header operativelyconnected to the lower ends of said second tubes for fluid flow; a steamand water drum operatively connected to the upper ends of said verticaltubular panel, and the upper ends of said first and third set of waterwall tubes for discharging steam and water into said drum; a firstdowntake pipe connecting said drum with said first distributing headerfor feeding water thereto; a second downtake pipe connecting said drumto said second distributing header for feeding water thereto; means forestablishing separate circulation of water through said first downtaketube, first distributing heater, first water wall tubes and back to saiddrum and through said second downtake tubes, second distributing header,second water wall tubes, intertional conduit means are provided forreturning water from said intermediate header to said first header.

References Cited in the file of this patent FOREIGN PATENTS Belgium Oct.15, 1952 France Oct. 26, 1955

